ZooKeeper only works when a majority of the participants are up. Since 2 out of 3 participants in your ensemble are down, ZooKeeper won't allow you to issue any commands, including a reconfiguration. You should have enough participants such that a situation where a majority is simultaneously down doesn't happen.
On Wed, Jun 15, 2016 at 4:33 PM, Nomar Morado <[email protected]> wrote: > Corrected typos > > Printing e-mails wastes valuable natural resources. Please don't print > this message unless it is absolutely necessary. Thank you for thinking > green! > > Sent from my iPhone > > > On Jun 15, 2016, at 9:31 AM, Nomar Morado <[email protected]> > wrote: > > > > This is what I have done so far: > > > > A,B,C are participants > > C,D are observers > > > > B,C are offline (crashed) > > > > I am trying to: > > > > 1. Remove C, D > > 2. Add C,D back as participants > > > > Will this work? > > > > At least in my testing (might be doing wrong) I am getting this error on > the first step and hence can't get forward: > > > > Client could not connect to reestablished quorum: giving up after 30+ > seconds > > > > > > I am passing the original server configure string to zk's reconfig > method. > > > > > > > > Thanks > > > > > > Printing e-mails wastes valuable natural resources. Please don't print > this message unless it is absolutely necessary. Thank you for thinking > green! > > > > Sent from my iPhone > > > >> On Jun 14, 2016, at 10:55 PM, Alexander Shraer <[email protected]> > wrote: > >> > >> Right, a quorum of participants from the old config is required to > process > >> any command, including reconfig, > >> and a quorum of participants from the new config is required for the > >> reconfig to even start. If there's no such connected > >> quorum an error NewConfigNoQuorum will be thrown. > >> > >> But there is one slightly confusing case where the error is thrown, > which > >> is explained in the doc: when you are > >> converting an observer to a participant and there is no quorum in the > new > >> config without counting that "future" participant. > >> So the server is connected, but since its not a participant we get the > >> error above. In that case, one first needs to > >> convert the observer to remove the observer and then add it back. The > >> detailed explanation is in the doc, look for > >> "Changing an observer into a follower". > >> > >> On Wed, Jun 15, 2016 at 1:17 AM, Camille Fournier <[email protected]> > >> wrote: > >> > >>> I'm finding the documentation quite confusing. I was under the > impression > >>> that quorum of some sort was needed to do a reconfig. Can you reconfig > when > >>> there is no quorum? > >>> > >>> *Progress guarantees:* Up to the invocation of the reconfig operation, > a > >>> quorum of the old configuration is required to be available and > connected > >>> for ZooKeeper to be able to make progress. Once reconfig is invoked, a > >>> quorum of both the old and of the new configurations must be available. > >>> > >>> *Adding servers:* Before a reconfiguration is invoked, the > administrator > >>> must make sure that a quorum (majority) of participants from the new > >>> configuration are already connected and synced with the current leader. > >>> > >>> > >>> > >>> On Tue, Jun 14, 2016 at 5:35 PM, Alexander Shraer <[email protected]> > >>> wrote: > >>> > >>>> This is needed only in case the target config doesn't have a quorum > which > >>>> are already followers in the old config > >>>> and are up. We need agreement from a quorum of the target config, but > >>>> observers aren't participating > >>>> in the voting protocol. > >>>> > >>>>> On Tue, Jun 14, 2016 at 7:35 PM, Michael Han <[email protected]> > wrote: > >>>>> > >>>>> This might help: > >>>>> https://zookeeper.apache.org/doc/trunk/zookeeperReconfig.html > section > >>>>> '*Changing > >>>>> an observer into a follower:'* > >>>>> "first invoke a reconfig to remove D from the configuration and then > >>>> invoke > >>>>> a second command to add it back as a participant (follower)." > >>>>> > >>>>> > >>>>> On Tue, Jun 14, 2016 at 8:53 AM, Nomar Morado < > [email protected]> > >>>>> wrote: > >>>>> > >>>>>> Hi > >>>>>> > >>>>>> I was trying to promote an observer into participant when ZK loses > >>>>> quorum - > >>>>>> but it seems that it does not allow to. > >>>>>> > >>>>>> Would you know how this can be accomplished without having to > recycle > >>>> ZK? > >>>>>> > >>>>>> I am using 3.5.0-alpha > >>>>>> > >>>>>> > >>>>>> Thanks. > >>>>> > >>>>> > >>>>> > >>>>> -- > >>>>> Cheers > >>>>> Michael. > >>> >
